Coil tubing may be used in the completion and well servicing process of an oil and gas well. Coil tubing is cost effective for both processes. Coil tubing does everything wire line services do, plus adds the ability to control the movement of fluid or gas in and out of the well.
The drilling process of the oil and gas well includes drilling a hole that typically ranges from 5½″ to 30″ into the earth to a desired depth. The hole is then lined with steel pipe called casing that extends from surface to the bottom of the well. The size of a drilling rig and its components make it very difficult and costly to use the drilling rig in the completion process. The personnel educated and trained for the drilling process are not always qualified for completion or well servicing work. Therefore, technology used for drilling is not necessarily applicable to the completion/well servicing side of the industry. The manufacturers of oil and gas industry equipment tend to specialize in the area of the industry or the other.
A blowout preventer (BOP) is a large piece of equipment used to seal, control and monitor oil and gas wells to prevent a blowout, which is the uncontrolled release of crude oil and/or natural gas from well, which is referred to as a blowout. BOPs are usually installed redundantly in stacks.
Blowout preventers were developed to cope with extreme erratic pressures and uncontrolled flow, also known as “formation kick” that can emanate from a well reservoir. Kicks can lead to a blowout, which is a potentially catastrophic event. In addition to controlling downhole pressure and the flow of oil and gas, BOPs are intended to prevent tubing, such as drill pipe and well casing, tools and drilling fluid from being blown out of the wellbore when a blowout threatens. BOPs safeguard the crew, rig, coiled tubing unit, and environment. BOPS also facilitate monitoring and maintenance of the well.
Two categories of blowout preventer are most prevalent, i.e., ram and annular. BOP stacks frequently utilize both types. Typically, wells are provided with at least one annular BOP stacked above several ram BOPs.
Blowout preventers are used on land wells, offshore rigs, subsea wells, and coiled tubing wireline operations. Land and subsea BOPs are secured to the top of the wellbore, known as the wellhead. BOPs on offshore rigs are mounted below the rig deck. Subsea BOPs are connected to the offshore rig above by a drilling riser that provides a continuous pathway for the drill string and fluids emanating from the wellbore. In effect, a riser extends the wellbore to the rig.
In a ram BOP, ram assemblies are provided to seal off an annulus surrounding a tubular member, and to seal off a well without tubing. Some ram assemblies have the ability to both severe the tubular member and to seal in the well. Typically, blades are affixed to opposing shear rams. The blades are driven together to completely shear the tubular member. The lower portion of the severed tubular member typically remains in the well beneath the shear rams, and the upper portion of the severed tubular member may be removed. A sealing element acting between the upper and lower shear blades or between each blade and the shear ram housing prevent fluid from escaping through the closed shear ram assembly.
A typical BOP has a round ram design that results in a relatively small front sealing surface.
Existing shear ram designs require different cutting blades for each size of coil tubing.
Existing BOPs have a bore pressure equalization system that utilizes a sealing system within the body of the BOP. When repairs are needed, the entire BOP is typically shopped.